In communication systems based on packet data communication, for example based on the Internet Protocol (IP), there is a need for a mobile communication node to be able to communicate with a fixed network infrastructure even when the mobile communication node moves such that it changes its point of attachment to the fixed network infrastructure: The mobile communication node could for example move such that it needs to change from communicating with a first access point belonging to a first Wireless Local Area Network (WLAN) to communicating with a second access point belonging to a second WLAN.
Mobile IPv6 and Mobile IPv4 are prior art protocols enabling such mobility in IPv6 based and IPv4 based networks, respectively. Mobile IPv6 is described e.g. in the document “Mobility Support in IPv6” by D. Johnson et al, RFC3775, published on the Internet by the Network Working Group of the Internet Engineering Task Force in June 2004. FIG. 1 shows a Mobile IPv6 based system and below is explained how mobility is achieved for a mobile communication node in such a Mobile IPv6 based system. The mobile communication node 105, which could be any communication device, for example a laptop or a mobile phone, has a home network 110, which has a Home Agent 111 and a Router 112. The mobile communication node has a stable home address belonging to the address space of the home network. FIG. 1 also shows a first foreign network 120 having at least one Access Point 121 and an access router 122, and a second foreign network 130 comprising an access router 132 and a correspondent node 135 connected to the Access Router 132. All networks are connected via an IP network 140, e.g. the Internet. In a scenario, the mobile communication node 105 is in its home network 110 and has established a connection to the correspondent node 135 connected to the second foreign network 130. The mobile communication node then moves from the home network to the first foreign network 120. The mobile communication node will then, according to Mobile IPv6, send a Binding Update (BU) message (which corresponds to a Registration Request in Mobile IPv4) via the first foreign network to the Home Agent 111 of the home network 110 informing the Home Agent of the mobile node's new address, i.e. it's care-of address in the first foreign network. Thereafter, the Home Agent 111 sends a Binding Acknowledge message (which corresponds to a Registration Reply in Mobile IPv4) to the mobile communication node and a tunnel is established between the mobile communication node and the Home Agent, via the IP network 140. On the mobile communication node endpoint the tunnel has the mobile communication node's care-of address as its outer address and the mobile communication node's home address as its inner address. The following traffic from the mobile communication node to the correspondent node 135 will then transit through the tunnel to the Home network and further to the correspondent node in the foreign network such that the previous connection between the mobile communication node and the correspondent node is preserved. Packets in the other direction, originating from the correspondent node 135, are addressed to the home address of the mobile communication node 105, intercepted by the Home Agent 111 and forwarded through the tunnel to the mobile communication node 105.
In another scenario not just a mobile communication node may be movable in relation to its home network, but a whole network, for example a network within a transport vehicle (e.g. bus, train or airplane). In this case, this so called moving network will have a router through which all communication nodes in the moving network can communicate. In the case of a moving network on e.g. an airplane, the moving network will comprise communication nodes, which may be different users' communication devices, such as laptops, mobile phones, PDAs (Personal Digital Assistants) etc., which communication nodes communicate wireless or wireline with a router within the airplane, such that all communication destined to an external address will pass via the router. A moving network may also be e.g. a Personal Area Network (PAN), wherein a PAN comprises all communication devices belonging to a user and situated within short range radio communication distance form each other, see for example co-pending patent application PCT/SE2004/001027. In this case, the communication devices in the PAN, called PAN devices, will communicate via a PAN device that has external access possibilities, e.g. a mobile phone having access to a GPRS network, such that the PAN device having external access possibilities works like a router for data originating from any PAN device and being directed to an address external of the PAN.
This document deals with mobility for a moving network, which is defined as a network that is mobile in relation to its home network. A moving network can change its point of attachment to a fixed infrastructure or it may have many points of attachment to a fixed infrastructure, but it is still able to communicate with its home network. A moving network is also characterized in that the nodes generating traffic are situated in the network. Such node in a moving network is called a moving network node. In this document, each node in the moving network or connected to the moving network that works like a router for data originating from a moving network node is defined as a mobile router. Examples of such mobile routers are: a PAN device working as a router in a PAN, and a router in a moving network on a vehicle. Note that a node may have both roles, i.e. being both a moving network node and a mobile router, for example a PAN device such as a mobile phone in a PAN.
“The Network Mobility (NEMO) Basic Support Protocol”, by Devarapalli et al, published June 2004 as an Internet Draft, which is a working document of the Internet Engineering Task Force, is a protocol that enables a moving network to attach to different points in the Internet. The protocol is an extension of Mobile IPv6 and allows session continuity for every communication node (or communication device) in the moving network as the network moves. It allows a mobile router to maintain a stable network prefix for a moving network, even as the mobile router changes its, and thus the moving network's, point of attachment to a fixed network infrastructure. This prefix stability is achieved through a solution similar to the mobile IPv6 solution, i.e. by making a home agent (HA) in the home network of the mobile router a fixed point of attachment for the Mobile Router (MR) and maintaining connectivity between the HA and the MR through a tunnel. The prefix is allocated from the address range of the home network, and can thus remain the same even as the MR and its network move. When the MR attaches to a network in a new location, it acquires a new care-of address, but its home address and prefix are unchanged. However, just like in Mobile IPv6 the MR has to register its new care-of address in the HA in order to maintain the tunnel between the Mobile Router and the Home Agent.
If, in the current NEMO solution, a bad tunnel is experienced, it will be replaced by a new tunnel by performing a new registration with the HA, this time with a different care-of address, unless the tunnel is re-established through the same interface and point of attachment, and possibly configured on a different interface, depending on the nature of the tunnel problems. If a communication node could get Internet access through multiple access media simultaneously, i.e. could have multiple tunnels established simultaneously, a data flow could be moved from a bad tunnel to a good tunnel much quicker than if only one tunnel at a time can be established. Also, for matters of cost, bandwidth, delay etc. it could be useful for a communication node to get Internet access through multiple simultaneous tunnels. However, the NEMO basic support protocol does not allow this because it allows only a single care-of address to be registered in the Home Agent (HA) for a certain Mobile Router (MR) at any one time. Multiple simultaneous care-of addresses are not allowed and thus multiple simultaneous accesses and MR-HA tunnels are not possible for a MR.
In the co-pending patent application PCT/SE2004/001578 by the same applicant, a procedure is suggested for managing different external access resources simultaneously accessible by a mobile router in a moving network, such that a network according to FIG. 2 based on a mobile IP-like solution can be established. In FIG. 2, which shows a moving network 201 situated e.g. on a train 200, a mobile router 204 of the moving network 201 has a home agent 216 in his home network 215 and a home address and one or more prefixes out of the address range of the home network 215. Moving network nodes 205, 206 attach to the moving network via access points 202, 203 such that they can communicate with the rest of the nodes in the moving network. When the moving network moves, the mobile router 204 may attach to a foreign network. In this case, a tunnel will be set up between the mobile router over the foreign network to the Home Agent 216 in the home network. In this way, according to mobile IP, the mobile router will get a care-of-address to its new location such that it can be reached by a correspondent node via its original address in the home network. In the network shown in FIG. 2, three tunnels are established simultaneously over three foreign networks and an IP network 214 between the Home Agent and the mobile router such that the mobile router has ability to access three different foreign networks 211, 212, 213. To the moving network this ability to access three different foreign networks can be seen as an ability to use three different external access resources: a WCDMA network 213, a satellite access network 212 and a GPRS network 211. To be able to fully make use of the three different external access resources, this procedure suggests that the mobile router controls the use of the different external access resources both for data packets sent in the direction to the home agent and for data packets sent from the home agent to the mobile router. To achieve this, the mobile router 204 classifies a data packet received from a moving network node 205, 206 based on information in the packet and selects an access resource for sending the packet based on the classification. The mobile router also sends implicit or explicit information to the home agent regarding routing of data packets from the home agent to the mobile router, such that the home agent classifies these data packets and selects access resource for sending the data packets based on the information received from the mobile router. With this procedure, a moving network node has the ability to use any of the external accesses of the mobile router simultaneously, such that it can quickly change access e.g. if one external access goes down. Since all decisions regarding which external access to use lies with the mobile router, the moving network nodes do not have to bother about the selection process and, consequently, do not have to have any extra functionality for selecting access.
The procedure described above only discusses a moving network having one mobile router with a plurality of external access possibilities. Although, it may happen that all external accesses present in an area are not handled by one and the same mobile router. For example, on a train there may be a fixed mobile router mounted in each railway-carriage. Also, for technical reasons, different external accesses may not be handled by the same mobile router. Therefore, to be able to give the moving network nodes in a moving network the ability to use all external accesses that are present in an area, there is a need for a function that can provide a moving network node with the ability to access external accesses provided by different mobile routers in a moving network such that a data packet can be sent from a moving network node and directed to an address external to the moving network via any of a number of external accesses provided by the different mobile routers. Also, there is a need to control the use of the different external accesses provided by the different mobile routers such that the external accesses are used in an efficient way.
The term flow or data flow used in the application is a loose term for a connection between two end nodes. A flow between a first and a second end node may have two directions: from the first node to the second node and vice versa. Thus, in the application, a data flow comprises an uplink part and a downlink part, wherein the uplink part is in the direction from the moving network node to the home agent (and further to the correspondent node), and the downlink part is in the direction from the home agent to the moving network node. A TCP (Transmission Control Protocol) connection is typically seen as a flow. A node can have multiple flows towards different correspondent nodes and also multiple flows towards the same correspondent node. Each flow comprises data packets. A flow is typically defined by the source and destination IP addresses and port numbers, plus the transport protocol in use, such as TCP or UDP (User Datagram Protocol). It is also possible to instead define a flow by its flow label (in IPv6) or its SPI (Security Parameter Index) together with the source and destination IP addresses, and the protocol in case of the SPI. The flow label is more specific than the port numbers and should have precedence over them. The SPI is used in IPsec (IP security as defined in RFC 2401 “Security Architecture for the Internet Protocol”), together with the destination IP address and the protocol to identify the security association, and the SPI-destination address-protocol triplet is typically used as a (unidirectional) flow identifier when the packet is encrypted and the port numbers are visible only to the receiving end-node. The terms link, access and external access used in the application are synonymous. One external access or link defines one possible way of getting external access from the moving network. There is one tunnel established between a Mobile Router and a Home Agent per external access.
The term Home Agent used in the application should be interpreted as any node in a home network working like a mobile anchor point to the moving network, i.e. facilitating communication from the moving network over an external network and the home network, such that the present invention can be used.